Wait, you've never heard of Pop Music Chart Day and the other national unofficial holidays that fall on Jan. 4 (National Trivia Day, Spaghetti Day, World Braille Day and Hypnotism Day, for the record)? Yeah, me neither, actually. But E! News pointed it out to me this morning, and since then, I've been thinking about what it actually means to be at the top of the pop game.

One of the quickest measures of success is, of course, the Billboard chart -- specifically the artists who've been able to climb to No. 1. But can you name the few, the proud who've managed such a feat this week historically over the past 10 years? OK, then prove it!